1. Field of the Invention
The present invention relates to a rubber composition which can improve both wear resistance and low heat-buildup property, which are properties antinomic to each other, and can be suitably used in various fields such as treads for tires, and to a tire in which low heat-buildup property (low fuel consumption) and tear resistance are improved without impairing wear resistance.
2. Description of the Related Art
Rubber compositions have been suitably used in various fields such as treads for tires and the like. When a rubber composition is used for a tread for a tire, it is desirable that the rubber composition is good in both wear resistance and low heat-buildup property, which are the properties antinomic to each other. In the prior art, carbon black having a high dibutyl phthalate absorption amount (DBP) was compounded to a rubber composition to improve wear resistance thereof. In this case, however, there was a drawback in that if the DBP was too large, wear resistance deteriorated and low heat-buildup property could not be sufficiently improved. A rubber composition which can simultaneously improve both wear resistance and low heat-buildup property, which are the properties antinomic to each other, and can improve these properties in a well balanced manner, has not been provided previously.
It is a first object of the present invention to provide a rubber composition which can improve both wear resistance and low heat-buildup property, which are properties antinomic to each other, can improve these properties in a well balanced manner, and can be suitably used in various fields such as treads for tires.
Further, it is desirable if a tread for a tire is good in both wear resistance and low heat-buildup property (low fuel consumption), which are the properties antinomic to each other. In the prior art, a compounding amount of carbon black was decreased to lower the heat-buildup property of a rubber composition which is used for a tread. In this case, however, a drawback arose in that wear resistance deteriorated. On the other hand, carbon black having a large DBP value was added to a rubber composition which was used for a tread for a tire so that wear resistance thereof was improved. In this case, however, there was a drawback in that if the DBP value was too large, wear resistance deteriorated and low heat-buildup property could not be sufficiently improved. In a case in which wear resistance was improved, although the life of a tire was extended, there was a drawback in that tears and the like were formed in the tire before a rubber composition was completely worn and thus the tire could not be used till the end of its expected life.
It is a second object of the present invention to provide a tire in which low heat-buildup property (low fuel consumption) and tear resistance are improved without impairing wear resistance.
Properties of a rubber composition are greatly influenced by interactions, such as physical bonding and chemical bonding, between a rubber component and carbon black which are compounded in the rubber composition. Carbon black is present in a rubber composition in the form of an aggregate dispersed therein. The present inventor has found that wear resistance and low heat-buildup property, which are the properties antinomic to each other, can be improved in a well balanced manner by improving dispersion of carbon black in a rubber composition, which can be done by controlling the form of the aggregate and the surface activity of the carbon black. Further, the present inventor has also found that even tear resistance can be improved by adding a hydrazide-based compound to the rubber composition.
The first aspect of the present invention for achieving the first object is a rubber composition comprising: at least one rubber component selected from natural rubber and a diene-based synthetic rubber; and a carbon black, wherein the carbon black has a dibutyl phthalate absorption amount (DBP) of 140 to 200 ml/100 g, an aggregate of the carbon black has a ratio (Dw/Dn) of a weight average diameter (Dw) to a number average diameter (Dn) of 1.80 to 2.40, and the carbon black has a specific tinting strength (Tint) and a nitrogen absorption specific surface area (N2SA) satisfying an inequality: Tint xe2x89xa70.100xc3x97(N2SA)+93.
The second aspect of the present invention for achieving the second object is a tire which has at least a tread, wherein the tread is formed of the rubber composition in accordance with the first aspect of the present invention.